The invention relates to an apparatus for controlling the heating of the passenger compartment in a motor vehicle. The apparatus includes a heat exchanger and a control element for regulating the flow rate of the heating medium and a controller which incorporates a room temperature sensor and a heating air current temperature sensor located at the air outlet of the heat exchanger. The controller also provides for an adjustable nominal temperature.
In a known system for heating the passenger compartment of a motor vehicle, the air outlet is controlled. In another control system, a series-connected room temperature sensor and exterior temperature sensor are coupled to an adjustable resistor. The electric circuit also includes the controller itself and an electromagnetic valve for operating a bypass conduit around the heat exchanger. Depending on the magnitudes of the variables measured by the sensors, the bypass valve is opened and closed. In this type of control, the flow rate of the heating medium is changed in dependence on the exterior and interior temperatures and an adjustable nominal value, and these three magnitudes are used in summation. However, this type of control does not permit an exact comparison with the nominal value corresponding to a desired temperature.